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A note on the white spot on the diving duck's chin

Posted by deheeg VIP , 4 Sep 2019

A black spot in our knowledge about the relationship of diving ducks?

Personal observations show that adult males of a number of diving ducks (genus Aythya) show a white spot under their chin, just at the base of their bill. Although not much is written about these spots in literature, museum skins show the same white spots in the same species. Canvasback, common pochard, ferruginous duck, Baer's pochard and Australian white-eyed pochard show this spot, to name a few. Other closely related ducks such as redhead, tufted duck, ring-necked duck and Madagascar pochard do not show this spot.

As this intrigues me, next questions came to my mind are:

Can the presence (or absence) of the white spot be lead back to only one Aythya-species?

If yes, how did it end up in the other species?

Is there a correlation between the morphologic character and the genetic relationship between species within the genus of Aythya.

Does anyone know more about this topic and can you recommend sources to me?